Male hosts drive infracommunity structure of ectoparasites

Abstract

We studied the co-occurrence of flea species in infracommunities of 16 rodents from four regions (South Africa, Tanzania, central Europe and western Siberia) using null models, and predicted that flea co-occurrences will be expressed more strongly in male than in female hosts. We examined patterns of co-occurrence (measured as the C score) in infracommunities of fleas that are parasitic on male and female hosts by comparing co-occurrence frequencies with those expected by chance. When a significant degree of nonrandomness in flea co-occurrences was detected, it indicated aggregative infracommunity structure. In Tanzanian rodents, no significant flea co-occurrences were detected in either male or female hosts. In a South African rodent, significant flea co-occurrences were not detected in males, but were found in females in some localities. In Palaearctic rodents, significant nonrandomness was detected either equally for males and females or more frequently in males than in females. Meta-analyses demonstrated that the frequency of the detection of nonrandomness in flea co-occurrences was significantly higher in male than in female hosts. The values of the standardized effect size (SES) for the C score differed significantly among host species, but not between host genders. When the Palaearctic hosts were analyzed separately, the effects of both host gender and species appeared to be significant, with the SES values for the C score in males being smaller than those in females. The strength of the gender difference in the manifestation of flea community structure increased with increasing gender difference in flea species richness, and with decreasing gender difference in flea prevalence for the Palaearctic hosts. We conclude that male hosts are the main drivers of flea infracommunity structure. However, the manifestation of gender bias in flea community structure varies among host species, and is likely determined by the pattern of species-specific spatial behavior.

Species co‐occurrences in ectoparasite infracommunities: Accounting for confounding factors associated with space, time, and host community composition

“…Although the relative importance of spatial (site, habitat), temporal (year), and host-associated factors (age and/or sex) explaining the variation in parasite distribution among individual hosts differed greatly among ectoparasite species and higher taxa, the incorporation of these effects into the models allowed us to elucidate general structural patterns of ectoparasite infra-and component communities. These patterns supported some, but not other, earlier findings (Krasnov et al, 2006avs Krasnov et al, 2011a, 2011b. In addition, some differences in the pattern of species co-occurrences between Slovakian and Argentinian ectoparasites may reflect the influence of (a) region-specific patterns of spatial variation and (b) the life histories of host species harbouring ectoparasites.…”

“…This is because we found that host sex and age explained only a minor, almost negligible, proportion of the variation in ectoparasite distribution among host individuals. Earlier reports on the higher frequency of positive ectoparasite species associations in male than in female hosts (Krasnov et al, 2011b) that invoked lower male immunocompetence (e.g. Olsen & Kovacs, 1996) thus appeared to be an artefact that probably arose because confounding factors were not accounted for in this earlier study.…”

“…For example the analysis of species co-occurrences in infracommunities encompassing several host species simultaneously may provide insight into the effect of the pattern of parasite associations in infracommunities on the pattern of parasite associations in component or compound communities (assemblages of parasites harboured by co-habitating conor heterospecific hosts, respectively). Second, earlier studies of parasite co-occurrences did not take into account confounding factors such as the temporal and spatial variation of parasite community structure and its dependence on host traits, such as sex or age (but see Krasnov et al, 2011b). In particular, the spatial and temporal heterogeneity of infestation, as well as trait variation among host individuals, may mask the true patterns and dependences of parasite community structure (e.g.…”

Parasite diversity of disease-bearing rodents of Southeast Asia: habitat determinants and effects on sexual size dimorphism and life-traits

“…trade-offs between investment in costly defenses and other life-traits such as reproduction are likely to occur and may intensify sexual competition and/or the degree of SSD (f) (Moore and Wilson, 2002;Krasnov et al, 2011Krasnov et al, , 2012. This also implies the existence of a negative relationship between relative spleen mass and relative testes size.…”

Variation in the prevalence and abundance of acanthocephalans in brown-nosed coatis Nasua nasua and crab-eating foxes Cerdocyon thous in the Brazilian Pantanal

“…Among mammals, males tend to have higher abundance, prevalence and parasite species richness than females (Poulin, 1996;Schalk and Forbes, 1997;Soliman et al, 2001; Rossin and Malizia, 2002). These trends have been related to sex-specific host behaviors, as well as distinct androgen levels, body mass differences, and higher levels of physiological stress (Brown et al, 1994;Arneberg et al, 1998;Moore and Wilson, 2002;Morand et al, 2004;Krasnov et al, 2011). Likewise, older hosts may have higher parasite loads due to the more extensive opportunity for exposure to the parasite throughout their lives (Anderson and Gordon, 1982;Anderson and May, 1991;Cooper et al, 2012;Hudson et al, 2002).…”